1. Field of the Invention
The present invention relates to a method of depositing an insulating film for forming an insulating film at a predetermined portion of a semiconductor device, at a focusing ion beam apparatus to be used in the method of depositing an insulating film.
2. Description of the Prior Art
On development of a semiconductor device, an operational check or a defective analysis of the device is essential. In such a case, it is necessary for the check to cut a part of wires to separate a part of a circuit or connect wires not connected to each other in a circuit. Recently a semiconductor has been highly integrated, and the minimum width or interval of the wire of the semiconductor device is now about 1 .mu.m. Thus, a fine process technology of a submicron unit is required to realize the process of cutting or connecting the wires.
Therefore, a focusing ion beam (hereinafter, called FIB) for performing a fine process of a submicron unit is recently used for the purpose. Also, an FIBIC repair apparatus for cutting or connecting the wires is sold on the market. Specifically, the FIBIC repair apparatus cuts the wires by sputter etching of, for example, a Ga (gallium) ion beam.
FIG. 1 is a schematic compositional diagram of a conventional focusing ion beam apparatus. In the same diagram, reference numeral 3 designates an ion optical tube in which a liquid metal ion source 1 for generating a focused ion beam 2 of Ga or the like is disposed. The beam 2 is irradiated on a sample placed in a sample room 4 directly facing the ion source 1 through a mass separator 6. Further, reference numeral 8 designates a table on which the sample 9 is placed. From a gas nozzle 5 disposed in the sample room 4, a gas 10 of a tungsten carbonyl (W(CO).sub.6) or the like is jetted onto the sample 9. Then, the gas is decomposed by the ion beam 2, so that a deposition film of tungsten or the like is formed on the sample 9. Additionally, reference numerals 7a, 7b respectively designate an opening and closing valve and a gas cylinder.
FIG. 2 is a cross section of an insulating film to be obtained by the conventional focusing ion beam apparatus and method of depositing an insulating film. In the conventional method of depositing an insulating film, the gallium (Ga) ion beam 2 is irradiated on the sample 9 in the state that a tungsten carbonyl (W(CO).sub.6) gas 11 is supplied to the sample 9 from the nozzle 5 disposed in the sample room 4. Thereby, the W(CO).sub.6 gas is decomposed, and the resultant tungsten (W) is deposited on the sample 9. Accordingly, a tungsten (W) wire can be formed on the sample 9 by irradiating the Ga ion beam on a desired area to connect between desired wires 12, 13.
However, in such a conventional method of depositing insulating film and a focusing ion beam apparatus, when a naked wire 17 is present between wires 15 and 16 to be connected to each other, the naked wire 17 should be coated by an insulating film before the wires 15 and 16 are connected. Conventionally, in such a case, the check was given up, or the wire 17 was coated with an insulating film in another process before the connection between the wires 15 and 16 by the conventional method. Accordingly, much time is required for the check if it be actually done, so that it is difficult to perfectly carry out the defective analysis and the operational check on a semiconductor device by the conventional method of depositing an insulating film and focusing ion beam apparatus.